A hyperbranched stationary phase for hydrophilic interaction liquid chromatography (HILIC) has been prepared by grafting polyethylenimine (PEI) onto silica gel (termed as PEI-Sil). Rich primary, secondary, and tertiary amino groups associated with PEI render its good hydrophility. More importantly, the hyperbranched structure of PEI molecule is greatly helpful in improving interaction with polar analytes. For several kinds of model polar compounds, including organic acids, nucleosides, nucleic acid bases, amino acids, cephalosporins, and non-reducing sugars, PEI-Sil demonstrated excellent separation performance in terms of running stability, reproducibility, and separation efficiency (e.g., plate count ~74,000/m). In addition, PEI-Sil also exhibited much better separation selectivity toward inorganic anions when operated in the mode of ion chromatography relative to a commercial amino propyl-bonded column.